This invention relates to high strength fibers of p-aramids having pendant carboxyl groups. The presence of these pendant groups imparts properties to the polymer and fibers or films thereof such as would enhance their reactivity, improve adhesion to matrix materials in reinforced composite structures or provide other characteristics.
The commercial importance of fiber reinforced composites has long been recognized. While the adhesion between certain reinforcing fibers and matrix polymer is excellent, others require the use of so-called "coupling agents" in order to improve the level of strength achieved through reinforcement. In some instances the use of coupling agents has not been satisfactory. Poly(p-phenylene terephthalamide) fiber finds extensive use as a reinforcement in composite structures. In accordance with this invention, the introduction of certain monomeric units in specified proportions in the polymer chain may reduce or eliminate the need for coupling agents in particular applications.